Dual Boot - SL7.x and Rocky8.x

I am currently running Scientific Linux 7.9 on my file and backup server and am in the process of installing Rocky Linux 8.4 on a reserved partition in dual boot arrangement. I’ve done a trial run of the Rocky installer (Boot image) and after selecting install partition I get the error message UEFI partition not selected.
Even though my firmware supports UEFI I am set up in legacy (CSM) mode and all disks are msdos. Can I ignore this error warning?
Since there is a lot of post install configuration to do I intend to keep SL linux boot loader and discover Rocky through the grub mkconfig process for now, therefore I won’t be installing the Rocky boot loader until it is configured to my liking.
I see other post where Rocky was installed to VM in legacy mode so I think it is possible but the VM set up did not support UEFI.


I’m not sure but I expect if Rocky sees that UEFI is possible, it will not allow it to do an MBR install. Check your BIOS to see if it’s configured for something like “legacy + UEFI” and perhaps ensure that it’s configured for legacy only. That way, if it cannot see UEFI at all as an option set in the BIOS it should let you install it in MBR mode. It’s not unique to Rocky, if it detects UEFI, other distros would also not allow install.

If motherboard is set to support legacy+UEFI, then it probably shows two boot options for Rocky media and if you did pick the UEFI option, then installer did boot in UEFI mode and will attempt install accordingly.

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OK, thanks for your clarification. I see in the firmware boot menu there are three options, one without UEFI which I’ve now selected and have booted to. I successfully selected the install partition w/o error message.


Just to follow up I successfully installed Rocky and have installed the Mate DE. Cockpit was essential in making that happen since I wouldn’t have been able to copy and paste the list of rpm’s w/o it. I’ve never used it before.
I can dual boot as intended.
I don’t see a mechanism to indicate my issue has been resolved.


What do you want to check/verify? You can dual-boot, so that issue is resolved. If you want to verify whether Rocky is using UEFI or not, you can do it by checking disk partitions, as well as see if there is a /boot/EFI. For example:

[root@rocky ~]# fdisk -l
Disk /dev/vda: 40 GiB, 42949672960 bytes, 83886080 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: FE808B7D-0C77-4ADA-823B-0DAAC57C8F13

Device       Start      End  Sectors  Size Type
/dev/vda1     2048  1050623  1048576  512M EFI System
/dev/vda2  1050624  2099199  1048576  512M Linux filesystem
/dev/vda3  2099200 83884031 81784832   39G Linux LVM

as you can see, there is an EFI partition, so this means my install is booting with EFI. If I was using MBR, then it would look something like this:

root@rocky:~# fdisk -l
Disk /dev/vda: 80 GiB, 85899345920 bytes, 167772160 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x8f377f4d

Device     Boot Start       End   Sectors Size Id Type
/dev/vda1  *     2048 167772126 167770079  80G 83 Linux

that is a test Linux install with MBR, and one single partition. If I was using EFI, then you would see a partition here. So if you check fdisk on your computer, and don’t see EFI, then it means you aren’t using it. You can also extra-verify this by seeing if you have a /boot/efi directory and if it is empty. A Rocky directory with UEFI, would look like this:

[root@rocky ~]# ls -hR /boot/efi

BOOT  rocky

BOOTX64.EFI  fbx64.efi

BOOTX64.CSV  fonts  grub.cfg  grubenv  grubx64.efi  mmx64.efi  shimx64.efi  shimx64-rocky.efi


if /boot/efi doesn’t exist, or it’s empty, then it means you aren’t using it.

I think the question is: How to mark this topic/thread/question “resolved”?

Perhaps you see tick-boxes on comments: Discourse Solved (Accepted answer plugin) - plugin - Discourse Meta

@jlehtone ah :rofl: /me thinking too technical I guess haha.